My invention is directed to an improved ac plasma display and more particularly to such a display having selective horizontal and vertical shifting capability.
A plasma panel is a display device comprised of a body of ionizable gas sealed within a nonconductive, transparent envelope. Alphanumerics, pictures, and other graphical data are displayed by controllably initiating glow discharges (also referred to as "gas discharges") at selected locations (sites) within the display gas. This is accomplished by setting up electric fields within the gas via appropriately arranged electrodes, or conductors.
The invention principally relates to so-called twin-substrate ac plasma panels which have the conductors embedded within dielectric layers disposed on two opposing nonconductive surfaces, such as glass plates. Typically, the conductors are arranged in rows on one plate and columns orthogonal thereto on the other plate. The overlappings, or crosspoints, of the row and column conductors define a matrix of discharge cells, or sites. Glow discharges (the ON-site condition) are initiated at selected crosspoints under the control of, for example, a digital computer.
My priorly filed copending patent application, known as Ser. No. 109,859, filed Jan. 7, 1980, now Pat. No. 4,328,489, is directed, inter alia, to a technique for providing self-shifting of the ON display sites of an ac plasma panel. In that application lateral shifting is accomplished using a four-phase technique operating in a manner to cause display site discharge transportation from an ON display site to a next adjacent site position. Using the four-phase technique, it is possible to connect together each fourth column conductor, resulting in the use of only four column drivers as opposed to one driver for each column conductor.
While my priorly taught technique operates properly, there still is required a separate driver for each of the row conductors. These individual drivers are necessary for the establishment of the visual display patterns, with each pattern typically consisting of a 13-row by 9-column matrix. Assuming a display having capability of 39 character lines, then 507 row conductors, each requiring driver circuitry, are necessary.
A major problem encountered in reducing this large number of row drivers stems from the fact that a display having four column drivers and only four row drivers would not have the capability of selectively introducing plasma discharge patterns to produce the desired intelligence on the display screen.
In an attempt to solve this problem, attention is directed to the establishment on one portion of the display, such as for example, along the bottom of the display, a staging area for the introduction onto the display of the desired information. Using this arrangement, the staging area would consist of several display rows and information in the form of discharge patterns would be introduced, as for example, in my prior invention, from the right side of the display. The introduced ON sites would then be shifted laterally across the display from site to site using the four-phase shifting technique. Once the information is in the desired lateral position within the staging area, the ON site would then be shifted upward to the proper display area for visual presentation to a viewer.
While, in theory, this approach solves the data introduction problem, it creates another problem which must be solved before the arrangement is practical. Because plasma panel row and column conductors are continuous, each column conductor of the lower staging area also extends through the upper display area. Thus, voltage pulses which are applied to the column conductors in the staging area for the purpose of lateral ON-site transportation will also be applied to the entire display column. Consequently, not only will information be shifted across the staging area, but any priorly displayed information within the viewing area will also be laterally shifted, thereby defeating the purpose of the staging area.